Transcranial Doppler measurements.

Transcranial Doppler ultrasonography (TCD) has served a useful purpose in further defining the pathophysiology of disordered cerebrovascular control after head injury. The evaluation of altered cerebrovascular responses in individual patients may be useful in their clinical management. TCD can be a clinically useful tool in the early diagnosis of a variety of complications that can occur in head-injured patients, such as vasospasm, markedly increased intracranial pressure (ICP), low cerebral perfusion pressure, carotid dissection, and disordered cerebral autoregulation. Although the TCD waveforms alone can alert clinicians to the presence of markedly increased intracranial pressure, these waveforms are not specific for predicting moderate ICP increases. Experienced interpreters can identify TCD waveforms that indicate the arrest of the cerebral circulation. Cerebral circulatory arrest can be a useful confirmatory finding in the diagnosis of brain death in questionable cases, and also can be used to shorten the observation period in those patients in whom organ donation is contemplated or discontinuation of ventilatory support and nursing care may be indicated.